The present invention relates to aromatic derivatives of formula (I) hereinafter reported and to iron complexes thereof, for the preparation of pharmaceutical compositions useful as normalising agents of the iron level.
Iron overload in the body, due to major defects in iron metabolism, such as genetic hemochromatosis and thalassemia, or due to minor causes, such as for example transfusions for hemolytic anemia, can bring the physiological defense reaction to saturation, thus having a toxic effect.
Such an effect is due to the expansion of the xe2x80x9cFree Iron Poolxe2x80x9d, which induces the production of oxygen active species responsible for the inactivation of cellular enzymes, for modifications in the membrane lipids, for DNA alterations, etc. (E. Cadenas, Ann. Rev. Biochem., 1989, 58: 79-110).
Therefore the consequences of the xe2x80x9cFree Iron Poolxe2x80x9d expansion can range from genotoxicity of the metal which causes the develop of tumours, to various organ pathologies, such as cirrhosis, diabetes, cardiopathy, hypogonadism and arthropathy.
Even in absence of an increase of the total iron in the body, an expansion of xe2x80x9cFree Iron Poolxe2x80x9d may happen, in association with many pathologic conditions, as for example neurodegenerative pathologies (M. Gassen et al., Pharmacol. Toxicol., 1997, 80(4): 159-166), atherosclerosis (A. J. Matthews et al., J. Surg. Res., 1997, 73(1): 35-40), ischaemic cardiopathy (T. P. Tuomainen et al., Circulation, 1998, 97(15): 1461-1466), chronic diseases of intestine (R. A. Floyd et al., Dig. Dis. Sci., October 1996, 41(10): 2078-86), and may cause the beginning or the development of the pathobiological event.
A strict correlation between alterations in the iron methabolism and HIV infections (J. R. Boelaert et al., Infect. Agents Dis., January 1996, 5(1): 36-46), as well as a connection between cardiotoxicity induced by iron and methabolism of antineoplastic agents in persons subjected to antitumoural therapy (G. Minotti et al., J. Clin. Invest., April 1995, 95(4): 1595-605), has been recently observed.
Moreover, it has been proved that the presence of xe2x80x9cFree Ironxe2x80x9d has a predominant role in the reactions bearing to the formation of free radicals and to the propagation of the damages due to free radicals, to which are associated for example inflammatory pathologies, such as arthritis and pyelonephritis (R. Gupta et al., Comp. Immunol. Microbiol. Infect. Dis., 1997, 20(4): 299-307), and senescence (M. C. Corti et al., Am. J. Cardiol., 1997, 79(2): 120-127).
At present, it is known the use of iron chelating agents in the treatment of systemic iron overload, associated to pathologies such as thalassemia or hemochromatosis.
The compounds used in such treatments show several drawbacks. For example, desferrioxamine, one of the substances more frequently used in this type of treatments, besides iron it binds many other important metals, such as aluminum, it is a very expensive product, it cannot be administered by oral route, and it has a half-life so short that continuous administration by subdermal infusion is necessary (R. J. Rothman et al., Mol. Pharmacol., 1992, 42: 703-710).
Other medicaments are known containing complexing agents of iron, such as deferiprone and derivatives thereof, showing a great bioavailability, but also a high toxicity caused just by their bioavailability, which bring for example to the onset of agranulocythemia, epathic fibrosis, etc. (N. F. Olivieri et al., N. Engl. J. Med., 1998, 339(7): 417-423).
Moreover, the medicaments, used up to now, have a dramatic effect on the cellular methabolism of iron, on which they produce a deep unbalance: as a matter of fact, they recall a great quantity of metal from the deposits of the organism and therefore they can be administered neither in the precox phases nor for sake of prophilaxys during hemochromatosis or thalassemia, nor in conditions in which the expansion of xe2x80x9cFree Iron Poolxe2x80x9d should be contrasted avoiding a variation in the quantity of the functional iron or of the iron stored in deposits.
It is therefore deeply felt the need of new compounds suitable for preparing pharmaceutical compositions, able to act as chelating agents of the total iron as well as of the xe2x80x9cFree Iron Poolxe2x80x9d, by removing it from cells and eliminating the resulting complex in urine.
It is felt as much the need of new pharmaceutical compositions for the treatment of pathologies to which a lack of iron in the body is associated.
Now the Applicant has surprisingly found that aromatic derivatives of formula (I): 
wherein:
R1 is 
xe2x80x83wherein R3 and R4 are selected from between H and OH, provided that R3 and R4 are not simultaneously H, and
R2 is H; or
R1 and R2, taken together, are 
xe2x80x83wherein R5 is selected from between CH3 and (CH2)5OH,
are able to bind stably the iron, in particular Fe(III).
Said compounds of formula (I) are suitable for the preparation of pharmaceutical compositions for oral administration, and show a high absorption and a high ability to permeate the biological membranes, in the form of free ligands as well as in the form of iron complexes.
Said pharmaceutical compositions are therefore useful for the treatment of all the pathological conditions related to an iron overload, in the case of an increase of the total iron as well as in the case of a relative increase in the iron level due to the expansion of the xe2x80x9cFree Iron Poolxe2x80x9d.
The iron complexes of the formula (I) compounds are also useful for the preparation of pharmaceutical compositions to be used in the treatment of pathologies related to a deficiency of iron, in the acute phase as well as for the chronic pathology.
It is therefore one object of the present invention the compounds of formula (I) for the preparation of pharmaceutical compositions for the use, in particular, as iron chelating agents, and the complexes thereof useful as iron release agents for hypoferremia.
Further object of the present invention are the compounds of formula (I) wherein
R1 is 
xe2x80x83wherein R3 is OH and R4 is H, OH, and R2 is H; or R1 and R2, taken together, are 
xe2x80x83wherein R5 is (CH2)5OH.
Features and advantages of compounds of formula (I) as iron chelating agents and of the iron complexes thereof according to the present invention will be illustrated in detail in the following description.
The present invention relates to compounds having the formula (I) above reported for the preparation of pharmaceutical compounds, in particular of pharmaceutical compounds for the use as iron chelating agents. The iron complexes of the present formula (I) compounds have therapeutic application too, as agents for the iron release.
The present formula (I) compounds, which can be easily prepared according to processes known in the art, show a high affinity for iron, in particular for Fe(III), giving stable complexes of such metal presenting different metal/ligand ratios. Concerning the preparation of said complexes, they are tipically prepared by reacting a compound of formula (I) with Fe(III) ions deriving from a ferric salt selected from the group consisting of inorganic salts of Fe(III), preferably perchlorate, chloride and sulphate, and more preferably perchlorate.
Said reaction is carried out in a solvent selected from the group consisting of acetone, chloroform, dichloromethane and aqueous solutions containing from 5 to 10% of dimethylsulphoxide, preferably in acetone.
Chelation experiments of iron have been carried out with the present formula (I) compounds wherein R1 and R2, taken together, are 
wherein R5 is selected from between CH3 and (CH2)5OH, and it has been found that they form a Fe(III) complex having a molar ratio ligand:metal equal to 2:1.
The preparation of said complex is preferably carried out at room temperature by reacting a compound of formula (I) with ferric perchlorate in acetone.
The stability constant of the Fe (III) complex with the compound of formula (I) wherein R1 and R2, taken together, are 
wherein R5 is CH3, has been measured by voltammetry with a Pt electrode as the working electrode and with a calomel electrode as the reference electrode, obtaining a stability constant equal to 3.0xc3x971010.
Analogous chelation experiments and measurements of the stability constants of the present complexes have been carried out for the other formula (I) compounds, obtaining analogous results.
The ability of the present formula (I) compounds and of iron complexes thereof for permeating the biologic membranes has been investigated by partition tests between n-ottanol and an aqueous solution of said compounds, which showed their greater affinity for the organic solvent.
In particular, partition experiments have been carried out between n-ottanol and an aqueous solution 20 mM of tris(hydroxymethyl)aminomethane chlorohydrate brought to pH=7.4 by adding sodium phosphate, obtaining values of the ripartition coefficient, expressed as the ratio between the concentration of the compound in the organic phase and that in the aqueous phase, tipically higher than 20, for the present formula (I) compounds as well as for the Fe (III) complexes thereof.
The compounds of formula (I) and iron complexes thereof according to the present invention can be formulated with pharmaceutically acceptable excipients and/or diluents, with the aim of preparing pharmaceutical compositions for the treatment of pathologies characterised by an overload or respectively by a lack of iron in the body.
For example, dimethylsulphoxide can be used as the diluent, and examples of excipients of possible use are methylcellulose, xcex2-cyclodextrins and polyethyleneglycol.
The concentration of the present formula (I) compound or that of the corresponding iron complexes in the pharmaceutical compositions ranges between 0.4 and 0.8% by weight with respect to the total weight of the composition.
Said compositions comprising the formula (I) compounds are efficient as iron chelating agents in the treatment of the systemic ironoverload, such as in the case of thalassemia and hemochromatosis, as well as in the treatment of the expansion of the xe2x80x9cFree Iron Poolxe2x80x9d.
The pharmaceutical compositions comprising the formula (I) compounds according to the present invention are therefore useful in the treatment of several pathologies to which an iron overload in the body is associated, comprising hemochromatosis, thalassemia, anemia associated to iron overload and conditions associated to secondary siderosis, neurodegenerative pathologies, such as Parkinson""s disease and Alzheimer""s disease, ischaemic cardiopathy, inflammatory chronic pathologies, such as arthritis, pyelonephritis, and inflammatory chronic diseases of the intestine, alterations in the metabolism of iron associated to HIV infections, cardiotoxicity due to doxorubicin and anthracyclines, atherosclerosis and senescence.
The pharmaceutical compositions comprising the iron complexes of the present formula (I) compounds are useful in the treatment of the pathologies to which a lack of iron in the body is associated, comprising sideropenic anemia in the acute phase as well as in the chronic form.